The functions of the excretory system in living organisms cannot be overemphasized. The excretory system helps remove the metabolic waste materials in order to regulate the chemical composition of fluids in the body. In single-celled organisms, they don't have a real organ system to remove their metabolic wastes.
However, they do this through the process known as diffusion. On the contrary, there is a specialized organ system in multicellular organisms that allow them to remove all their metabolic wastes out of their body system. The excretory system helps regulate the normal amount of nutrients, salts, and water in the body.
In multicellular organisms, especially vertebrates, the organs of the body that help in removing the wastes are skin, kidneys, lungs, and liver. However, it is important to note that all animals use different routes to excrete their wastes. Invariably, the excretory system helps remove excretory products such as nitrogen wastes from the body